Caribou, water, and ice - fine-scale movements of a migratory arctic ungulate in the context of climate change.

Leblond M, St-Laurent MH, Côté SD - Mov Ecol (2016)

Bottom Line:
Although ice phenology did not change significantly during our study, climate projections indicated that ice availability could decrease considerably before the end of the century, generating a ~28 % increase in distance travelled by caribou during the early spring and fall migrations.We demonstrated that ice availability influenced the movements of a migratory arctic ungulate.The long-term conservation of wide-ranging species will ultimately depend on our ability to identify the fine-scale behavioural reactions of individuals to broad-scale changes in climate and land use.

Background: Freshwater lakes and rivers of the Northern Hemisphere have been freezing increasingly later and thawing increasingly earlier during the last century. With reduced temporal periods during which ice conditions are favourable for locomotion, freshwater bodies could become impediments to the inter-patch movements, dispersion, or migration of terrestrial animals that use ice-covered lakes and rivers to move across their range. Studying the fine-scale responses of individuals to broad-scale changes in ice availability and phenology would help to understand how animals react to ongoing climate change, and contribute to the conservation and management of endangered species living in northern environments. Between 2007 and 2014, we equipped 96 migratory caribou Rangifer tarandus caribou from the Rivière-aux-Feuilles herd in northern Québec (Canada) with GPS telemetry collars and studied their space use. We measured contemporary (digital MODIS maps updated every 8 days, 2000-2014) and historical (annual observations, 1947-1985) variations in freshwater-ice availability and evaluated the concurrent responses of caribou to these changes.

Results: Ice had a positive influence on caribou movement rates and directionality, and caribou selected ice and avoided water when moving across or in the vicinity of large water bodies. When ice was unavailable, caribou rarely swam across (6 % of crossings) and frequently circumvented water bodies for several km. Although ice phenology did not change significantly during our study, climate projections indicated that ice availability could decrease considerably before the end of the century, generating a ~28 % increase in distance travelled by caribou during the early spring and fall migrations.

Conclusions: We demonstrated that ice availability influenced the movements of a migratory arctic ungulate. Warmer air temperatures in the Arctic will undoubtedly modify the phenology of ice forming on freshwater lakes and rivers. If migratory caribou are unable to adjust the timing of their migrations, they could be forced to circumvent unfrozen water bodies more frequently and over broader areas, which may increase the distance, time, and energy they use to reach wintering areas. The long-term conservation of wide-ranging species will ultimately depend on our ability to identify the fine-scale behavioural reactions of individuals to broad-scale changes in climate and land use.

Fig1: Study area in Northern Québec showing the range of the Rivière-aux-Feuilles caribou herd. We delineated the range using a 100 % minimum convex polygon encompassing caribou locations from 2007 to 2014. The largest water bodies used to study caribou responses to ice and water (as well as Lake Nichicun, see Additional file 3) appear in blue. All other water bodies in the province appear in light grey. Inserts show the location of our study area (top-left) and the steps performed by caribou during this study (bottom-left). Overlaid over observed steps (green lines) are the approximate trajectories of the fall migrations (red arrow), winter displacements (blue arrow), and spring migrations (black arrow) performed by caribou

Mentions:
The RAF caribou herd ranged over >630 000 km2 across Northern Québec, Canada (Fig. 1). Females gave birth in the Arctic tundra of the Ungava Peninsula (61°N, 74°W), generally between early and mid-June. In October–December, caribou undertook a long migration across the taiga and into the northern fringe of the boreal forest, where they fed on arboreal and terrestrial lichens (mostly Cladonia, Cetraria, and Usnea) found in open black spruce (Picea mariana) stands [33]. In April, they left their wintering ranges and initiated a migration back to the calving grounds. Across this entire journey, they coped with severe climatic conditions typical of arctic and subarctic regions [34]. In the southern part of the caribou range, a series of hydroelectric infrastructures were built during Hydro-Québec’s James Bay Project in the 1970s and 1980s. Many structures were built on La Grande River, along which several natural lakes were converted into some of the largest artificial reservoirs in the region (Fig. 1).Fig. 1

Fig1: Study area in Northern Québec showing the range of the Rivière-aux-Feuilles caribou herd. We delineated the range using a 100 % minimum convex polygon encompassing caribou locations from 2007 to 2014. The largest water bodies used to study caribou responses to ice and water (as well as Lake Nichicun, see Additional file 3) appear in blue. All other water bodies in the province appear in light grey. Inserts show the location of our study area (top-left) and the steps performed by caribou during this study (bottom-left). Overlaid over observed steps (green lines) are the approximate trajectories of the fall migrations (red arrow), winter displacements (blue arrow), and spring migrations (black arrow) performed by caribou

Mentions:
The RAF caribou herd ranged over >630 000 km2 across Northern Québec, Canada (Fig. 1). Females gave birth in the Arctic tundra of the Ungava Peninsula (61°N, 74°W), generally between early and mid-June. In October–December, caribou undertook a long migration across the taiga and into the northern fringe of the boreal forest, where they fed on arboreal and terrestrial lichens (mostly Cladonia, Cetraria, and Usnea) found in open black spruce (Picea mariana) stands [33]. In April, they left their wintering ranges and initiated a migration back to the calving grounds. Across this entire journey, they coped with severe climatic conditions typical of arctic and subarctic regions [34]. In the southern part of the caribou range, a series of hydroelectric infrastructures were built during Hydro-Québec’s James Bay Project in the 1970s and 1980s. Many structures were built on La Grande River, along which several natural lakes were converted into some of the largest artificial reservoirs in the region (Fig. 1).Fig. 1

Bottom Line:
Although ice phenology did not change significantly during our study, climate projections indicated that ice availability could decrease considerably before the end of the century, generating a ~28 % increase in distance travelled by caribou during the early spring and fall migrations.We demonstrated that ice availability influenced the movements of a migratory arctic ungulate.The long-term conservation of wide-ranging species will ultimately depend on our ability to identify the fine-scale behavioural reactions of individuals to broad-scale changes in climate and land use.

Background: Freshwater lakes and rivers of the Northern Hemisphere have been freezing increasingly later and thawing increasingly earlier during the last century. With reduced temporal periods during which ice conditions are favourable for locomotion, freshwater bodies could become impediments to the inter-patch movements, dispersion, or migration of terrestrial animals that use ice-covered lakes and rivers to move across their range. Studying the fine-scale responses of individuals to broad-scale changes in ice availability and phenology would help to understand how animals react to ongoing climate change, and contribute to the conservation and management of endangered species living in northern environments. Between 2007 and 2014, we equipped 96 migratory caribou Rangifer tarandus caribou from the Rivière-aux-Feuilles herd in northern Québec (Canada) with GPS telemetry collars and studied their space use. We measured contemporary (digital MODIS maps updated every 8 days, 2000-2014) and historical (annual observations, 1947-1985) variations in freshwater-ice availability and evaluated the concurrent responses of caribou to these changes.

Results: Ice had a positive influence on caribou movement rates and directionality, and caribou selected ice and avoided water when moving across or in the vicinity of large water bodies. When ice was unavailable, caribou rarely swam across (6 % of crossings) and frequently circumvented water bodies for several km. Although ice phenology did not change significantly during our study, climate projections indicated that ice availability could decrease considerably before the end of the century, generating a ~28 % increase in distance travelled by caribou during the early spring and fall migrations.

Conclusions: We demonstrated that ice availability influenced the movements of a migratory arctic ungulate. Warmer air temperatures in the Arctic will undoubtedly modify the phenology of ice forming on freshwater lakes and rivers. If migratory caribou are unable to adjust the timing of their migrations, they could be forced to circumvent unfrozen water bodies more frequently and over broader areas, which may increase the distance, time, and energy they use to reach wintering areas. The long-term conservation of wide-ranging species will ultimately depend on our ability to identify the fine-scale behavioural reactions of individuals to broad-scale changes in climate and land use.